Properties Of MoS2 Research Articles

A Kirigami Inspired Atomistic Investigation on Enhancement of Mechanical Properties of Single-layer MoS

A Kirigami Inspired Atomistic Investigation on Enhancement of Mechanical Properties of Single-layer MoS

MoS2 based nanomaterials: Advanced antibacterial agents for future.

Bacterial infections are yet another serious threat to human health. Misuse or overuse of conventional antibiotics has led to the arrival of various super resistant bacteria along with many serious side effects to human body. In this exigent circumstance, the use of nanomaterial based antibacterial agents is one of the most appropriate solutions to fight against bacteria thereby causing an inhibition to bacterial proliferation. Recent studies show that, due to the large surface area, high biocompatibility, strong near-infrared (NIR) absorption and low cytotoxicity, molybdenum disulphide (MoS2), an extraordinary member in the transition metal dichalcogenides (TMDs) is extensively explored in the obliteration of many drug resistant bacteria, photothermal therapy and drug delivery. MoS2 based nanomaterials can effectively prevent bacterial growth through many mechanisms. Through this review, we have tried to provide an inclusive knowledge on the recent progress of antibacterial studies in MoS2 based nanomaterials including MoS2 nanosheets, nanoflowers, quantum dot (QD), hybrid nanocomposites and polymer nanocomposites. Moreover, toxicity of MoS2 based nanomaterials is described at the end of the review.

Molecular Orbitals Support Energy-Stabilizing "Bonding" Nature of Bader's Bond Paths.

Our MO-based findings proved a bonding nature of each density bridge (DB, or a bond path with an associated critical point, CP) on a Bader molecular graph. A DB pinpoints universal physical and net energy-lowering processes that might, but do not have to, lead to a chemical bond formation. Physical processes leading to electron density (ED) concentration in internuclear regions of three distinctively different homopolar H,H atom-pairs as well as classical C-C and C-H covalent bonds were found to be exactly the same. Notably, properties of individual MOs are internuclear-region specific as they (i) concentrate, deplete, or do not contribute to ED at a CP and (ii) delocalize electron-pairs through either in- (positive) or out-of-phase (negative) interference. Importantly, dominance of a net ED concentration and positive e--pairs delocalization made by a number of σ-bonding MOs is a common feature at a CP. This feature was found for the covalently bonded atoms as well as homopolar H,H atom-pairs investigated. The latter refer to a DB-free H,H atom-pair of the bay in the twisted biphenyl (Bph) and DB-linked H,H atom-pairs (i) in cubic Li4H4, where each H atom is involved in three highly repulsive interactions (over +80 kcal/mol), and (ii) in a weak attractive interaction when sterically clashing in the planar Bph.

Raman tensor of layered MoS2.

Raman tensors, one of the basic physical properties of ${{\rm MoS}_2}$MoS2, are rarely reported. Here, angle-resolved polarized Raman scatterings on basal and cross planes of layered ${{\rm MoS}_2}$MoS2 were carried out using the geometry configuration of parallel polarization, and the Raman tensors of three optical vibration modes were systematically studied. As a polar vibration mode, the differential polarizability of the ${{\rm A}_{1{\rm g}}}$A1g mode corresponding to the Raman tensor along the $c$c direction is larger than that along the $a$a direction. In addition, it is also larger than that formed by ${{\rm E}_{2{\rm g}}}$E2g and ${{\rm E}_{1{\rm g}}}$E1g modes. All the experimental results above are beneficial to the understanding of inelastic light-scattering process of ${{\rm MoS}_2}$MoS2.

Facile Synthesis of Ultra‐Small Few‐Layer Nanostructured MoSe2 Embedded on N, P Co‐Doped Bio‐Carbon for High‐Performance Half/Full Sodium‐Ion and Potassium‐Ion Batteries

Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe2 embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe2 /NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g-1 at 100 mA g-1 after 100 cycles) and impressive long-term cycling performance (192 mAh g-1 at 5 A g-1 even after 1000 cycles) in SIBs, which are some of the best properties of MoSe2 -based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe2 /NP-C-2 composite anode with a Na3 V2 (PO4 )3 cathode also exhibits a satisfactory capacity of 215 mAh g-1 at 500 mA g-1 after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g-1 at 1 A g-1 even after 250 cycles for PIBs.

Nonlinear optical performance of few-layer molybdenum diselenide as a slow-saturable absorber

Two-dimensional transition metal dichalcogenides are considered promising materials for next-generation photonics and nano-optical devices. Although many previous reports have shown saturable absorption of molybdenum diselenide (MoSe2), these nonlinear optical (NLO) properties of MoSe2 were measured in separate works and under different conditions with their hot-carrier relaxations. Here, we conducted a series of coherent studies on the NLO properties of few-layer MoSe2 via open-aperture Z-scan and degenerate pump-probe techniques. These measurements were taken to test the materials’ capabilities as a slow-saturable absorber. A slow-absorber model was employed to analyze the NLO measurements, and the results show that the NLO modulation depth was modeled to be 7.4% and 15.1% for the linear absorption coefficients of 5.22 cm−1 and 6.51 cm−1, respectively. The corresponding saturated intensities were modeled to be 39.37 MW/cm2 and 234.75 MW/cm2, respectively. The excitation carrier recovery time of few-layer MoSe2 was measured by degenerate pump-probe techniques to be ∼220 ps. These nonlinear optical performances make it a promising slow-saturable absorber for passive mode locking in femtosecond lasers.

The effect of point defect on mechanical properties of MoSi2

The effect of point defect on mechanical properties of MoSi2 has been investigated by the first-principles. The elastic constants, mechanical modulus, hardness and thermodynamic properties of MoSi2 with four different single point defects have been calculated. By comparing with the defect-free MoSi2, it is found that the bulk modulus/shear modulus ratio (B/G) of MoSi2 with a single point defect increases slightly while the Debye temperature decreases drastically, which indicates that MoSi2 with some point defects have relatively good ductility. The calculated three-dimensional (3D) contours of elastic modulus and these projections on the (001) and (010) planes show that the directionality of Young’s modulus and shear modulus is unapparent for MoSi2 with a point defect (V[Formula: see text] and Mo[Formula: see text]) but it is relatively obvious for MoSi2 with V[Formula: see text] and Si[Formula: see text]. It suggests that V[Formula: see text] and Si[Formula: see text] can strengthen the anisotropy in elasticity. The electronic properties of C11[Formula: see text] MoSi2 with different single point defects have been studied to reveal further the influencing mechanism of point defect on mechanical properties. This work should help reveal the interrelation between intrinsic defects and service performance of MoSi2.

The Density of MoSi2 Electron States for the Amorphous Film

The density of MoSi2 electron states for the amorphous film has been calculated. An electron states at the top of valence band for this material are provided d electrons of molybdenum, p electrons of silicon and p electrons of molybdenum. d electrons of molybdenum are significant especially for physical properties of MoSi2.

Synthesis and Properties of MoSi2–MoB–SiC Ceramics

MoB and SiC particulate reinforced MoSi2 matrix composites were synthesized in situ from Mo, Si, and B4C powder mixtures by self‐propagating high‐temperature synthesis (SHS). The SHS MoSi2–MoB–SiC products were vacuum hot‐pressed (HPed) at 1400°C for 90 min to fabricate high‐density (> 97.5% relative density) bulk composites. Microstructure refinement and improvements in the Vickers hardness and fracture toughness of the HPed composites were observed with increasing B4C content in the reaction mixture. The HPed composite of composition MoSi2–0.4MoB–0.1SiC exhibited grain size of 1–5 μm, Vickers hardness of 12.5 GPa, bending strength of 537 MPa, and fracture toughness of 3.8 MPa.m1/2. These excellent mechanical properties indicate that MoB and SiC particulate reinforced MoSi2 composites could be promising candidates for structural applications.

Mechanical and electrical properties of MoSi2–RSiC composites via a combination of phenolic resin infiltration–pyrolysis and MoSi2–Si–Ti alloy-activated melting infiltration composite processes

A three-dimensional interpenetrated network structure composite was designed and prepared via a combination of phenolic resin infiltration-pyrolysis and MoSi2–Si–Ti alloy-activated melting infiltration processes to effectively merge the desirable properties of MoSi2 and RSiC. Influence of infiltration temperature on the microstructure, mechanical and electrical properties of the composites was examined. Almost dense MoSi2–RSiC composites with the designed structure were obtained at 1900°C. Formation of the gradient interface modified the interface combination and enhanced the mechanical and electrical properties of the composite. Flexural strength of the composites reached approximately 114.262 MPa (room temperature) and 128.392 MPa (1400°C), respectively, indicating corresponding increases of 37.08 and 35.69% compared with the RSiC matrix. Volume resistivity decreased to 57.63 mΩ cm, nearly five orders of magnitude lower than that of RSiC. Influence of the interpenetrated network structure and interface combination on the electrical conductivity behaviour of the composites was discussed via a modified mixture rule.

Mo1791 Ulcerative Colitis-Associated Escherichia coli Colonize the Ileum and Cecum of Infected Mice by Adhering to the Intestinal Epithelium

Background: Monocytes (Mo) play an important role in the pathogenesis of intestinal mucosal inflammation. This study aims to investigate into the mechanism whereby the intestinal epithelial cell (IEC)-derived thrombospondin 1 (TSP1) modulates Mo properties and regulates intestinal inflammatory responses. Methods: The production of TSP1 by IEC was evaluated by quantitative real-time PCR and Western blotting. The properties of Mos were analyzed by flow cytometry. A mouse model of colitis was established to assess the role of epithelium-derived TSP1 induced by C. butyricum in the suppression of intestinal inflammation. Results: The results demonstrated that mouse IECs expressed TSP1, which was markedly upregulated by butyrate or feeding with C. butyricum. Coculture the butyrateprimed IECs and Mos or exposure of Mos to TSP1 in the culture induced expression of transforming growth factor (TGF)-β in Mos. These TGF-β+ Mos had tolerogenic properties that could promote generation of inducible regulatory T cells. Importatnly, adoptive transfer with TSP1-primed Mos, or feeding C. butyricum could prevent experimental colitis in mice. Conclusions: C. butyricum induces IECs to produce TSP1 and induces generation of TGFβ+ Mos, which further suppress experimental colitis in mice. The results implicate that administration of C. butyricum or butyrate may have the potential to ameliorate chronic intestinal inflammation through inducing immune suppressive Mos.

Mo1790 Butyrate Induces Intestinal Epithelial Cell to Express Thrombospondin 1 and Suppress Intestinal Mucosal Inflammation

Background: Monocytes (Mo) play an important role in the pathogenesis of intestinal mucosal inflammation. This study aims to investigate into the mechanism whereby the intestinal epithelial cell (IEC)-derived thrombospondin 1 (TSP1) modulates Mo properties and regulates intestinal inflammatory responses. Methods: The production of TSP1 by IEC was evaluated by quantitative real-time PCR and Western blotting. The properties of Mos were analyzed by flow cytometry. A mouse model of colitis was established to assess the role of epithelium-derived TSP1 induced by C. butyricum in the suppression of intestinal inflammation. Results: The results demonstrated that mouse IECs expressed TSP1, which was markedly upregulated by butyrate or feeding with C. butyricum. Coculture the butyrateprimed IECs and Mos or exposure of Mos to TSP1 in the culture induced expression of transforming growth factor (TGF)-β in Mos. These TGF-β+ Mos had tolerogenic properties that could promote generation of inducible regulatory T cells. Importatnly, adoptive transfer with TSP1-primed Mos, or feeding C. butyricum could prevent experimental colitis in mice. Conclusions: C. butyricum induces IECs to produce TSP1 and induces generation of TGFβ+ Mos, which further suppress experimental colitis in mice. The results implicate that administration of C. butyricum or butyrate may have the potential to ameliorate chronic intestinal inflammation through inducing immune suppressive Mos.

Thrombospondin 1 Modulates Monocyte Properties to Suppress Intestinal Mucosal Inflammation

Monocytes (Mos) play an important role in the pathogenesis of intestinal mucosal inflammation. This study aims to investigate the mechanism by which the intestinal epithelial cell-derived thrombospondin 1 (TSP1) modulates Mo properties and regulates intestinal inflammatory responses. In this study, the production of TSP1 by intestinal epithelial cells was evaluated by quantitative real-time PCR and Western blotting. The properties of Mos were analyzed by flow cytometry. A mouse model of colitis was created to assess the role of epithelium-derived TSP1 in the suppression of intestinal inflammation. The results demonstrated that mouse intestinal epithelial cells (IECs) expressed TSP1, which was markedly upregulated by butyrate or feeding with Clostridium butyricum. Coculture of the butyrate-primed IECs and Mos or exposure of Mos to TSP1 in the culture induced the expression of transforming growth factor (TGF)-β in Mos. These TGF-β⁺ Mos had tolerogenic properties that could promote generation of inducible regulatory T cells. Adoptive transfer with TSP1-primed Mos, or feeding C. butyricum could prevent experimental colitis in mice. In summary, C. butyricum induces intestinal epithelial cells to produce TSP1 and induces TGF-β⁺ Mos, which further suppress experimental colitis in mice. The results implicate that the administration of C. butyricum or butyrate may have the potential to ameliorate chronic intestinal inflammation through inducing immunosuppressive Mos.

Anti-ablation properties of MoSi2–W multi-layer coating system deposited by atmospheric plasma spray

Carbon fibre reinforced carbon (C/C) composites have become an important material for hyper thermal conditions and have been widely used in aerospace and aviation industry. However, the composites will be ablated above 723 K in an oxygen-containing atmosphere. The MoSi2–W multi-layer anti-ablation coating system was deposited by atmospheric plasma spray. The supersonic flame caused by kerosene and oxygen was selected to examine the property of the coatings. Samples of three groups were ablated by the flame at 1600°C. The speed of gas flow was 850 m s–1. The MoSi2–W multi-layer anti-ablation coating system can protect the graphite matrix effectively. The products of ablation include SiO2, Mo5Si3 and MoO3. With the prolongation of time, the aggregates sinter and grow up. The network structure of the coatings is caused by the evaporation of MoO3 and loss of SiO2.

The Effects of Particle Size and Morphology of Raw Materials on the Properties of MoSi<sub>2</sub> Synthesized by SHS

In this work, the influences of the particle size and morphology of raw materials on the formation of MoSi2 by self-propagating high-temperature synthesis (SHS) were investigated. A series of Si powders with different particle sizes and Mo powders with different morphologies were obtained by grinding for 1, 5 and 10 hours, respectively. X-ray diffraction pattern characterization (XRD) and scanning electron microscopy (SEM) were used to characterize the samples. It was found that, the phase compositions and morphologies of the combustion products depended on the particle size and morphology of the raw materials. The particle sizes of Si powders decreased with increasing the grinding time, and a secondary phase of Mo5Si3 was detected in the obtained MoSi2 powders when the smallest particle size of Si powders was about 1μm. While, the particle sizes of Mo powders increased with increasing the grinding times, and the obtained MoSi2 showed massive flaky structures, which were similar to the morphologies of Mo particles.

退火温度对MoS2纳米薄膜特性影响研究

本文主要采用化学气相沉积法，以MoS2饱和溶液为原料，利用氩气为输运气体，携带MoS2蒸汽进入反应室，在Si衬底上制备大面积均匀的MoS2超薄薄膜，并分析了不同的退火温度对于薄膜表面形貌、吸收特性以及电学特性的影响。研究发现，经过850℃退火的二硫化钼薄膜平整，厚度和晶粒尺寸也逐渐均匀。另外，随退火温度升高，MoS2超薄膜反射率降低，可显著提高器件光伏效应和光电转换效率，制备高效率的MoS2/Si异质结太阳能电池。退火还可以改善薄膜的电学特性，经过850℃退火的薄膜，其导电率达到了2.848 × 10-4，霍尔迁移率高达6.42 × 102 cm 2V-1s-1，可用于制造超低待机功率的场效应管。通过分析不同退火温度对纳米MoS2薄膜光电特性的影响，得出纳米MoS2薄膜的最佳退火温度为850℃，这促进了MoS2纳米电子器件的发展，推进了MoS2在光电子领域以及信息技术方面的广泛应用。 Molybdenum disulfide (MoS2) thin films were deposited on Si substrates with MoS2 saturated solution as a raw material carried by argon (Ar) gas by means of chemical vapor deposition. We have analyzed the influence of different annealing temperatures on surface morphology of films, absorption characteristics and electrical properties. We found that MoS2 thin film annealled at 850C was characteristic of more smooth and symmetrical as compared to that of the unannealed sample. At the same time, the optical reflectivity apparently reduced, which indicated that annealing can effectively improve photovoltaic effect and photoelectric conversion efficiency, and can be used for fabricating solar cell. In addition, we found that the electrical properties of MoS2 thin films had also been enhanced after annealing. We noted that the conductivity and the carrier mobility were up to 2.848 × 10-4 and 6.42 × 102 cm 2V-1s-1, when annealing at 850C, which shows promising potential for low power field effect transistor. Analyzing the influence of different an- nealing temperatures on photoelectric properties of MoS2 nanometer thin films, we demonstrated that the best annealing temperature was 850C, which enhanced the applications of MoS2 in the field of photoelectron and information techno- logy.

Investigation on effect of alloying elements on mechanical properties of MoSi2 by first principle calculation

The influence of substitutional alloying elements (Al, Nb and W) on the mechanical properties of MoSi2 with both C11b and C40 structures was explored by first principles calculations. Using the shear modulus/bulk modulus ratio (G/B), Poisson’s ratio and Peierls stress, the change in the mechanical properties of the C40 and C11b structured MoSi2 due to the addition of the solute atom has been investigated. The results showed that the ductility of C11b MoSi2 was increased by alloying with the elements (Al and Nb) that form a C40 structured disilicide but decreased by alloying with the elements (W) that form a C11b structured disilicide. In contrast, the effect of alloying elements on the ductility of C40 MoSi2 showed a reverse trend to that of C11b MoSi2.

Cyclic Oxidation Behaviour of MoSi<sub>2</sub> and MoSi<sub>2</sub>-Si<sub>3</sub>N<sub>4</sub> Composites for Aircraft Gas Turbine Elements

Pest oxidation phenomena is the major drawback of MoSi2 for the applications of this material over gas turbine elements. Therefore, addition of Si3N4 does not only eliminate the structural disintegration behaviour which can only be observed between relatively low temperatures (673-873 K) but also improves the fracture toughness at elevated temperatures. In this study, after giving some significant properties of MoSi2, effect of processing conditions to microstructural morphology and oxidation characteristics at gas turbine operating temperatures will be discussed within a composit approach.

Metallic and ferromagnetic edges in molybdenum disulfide nanoribbons

The magnetic and electronic properties ofMoS2 nanoribbons with zigzag and armchair edges are investigated using LSDA-DFT.We found that the properties of the nanoribbons are very different from bulkMoS2 due to edge states. Armchair nanoribbons could be metallic and exhibit a magneticmoment; however, when passivating with hydrogen, they become semiconducting. Zigzagnanoribbons are metallic and exhibit unusual magnetic properties regardless ofpassivation. Our results could explain the recent evidence of ferromagnetism in flatMoS2 clusters, and motivatethe synthesis of novel MoS2 nanosystems.

Effect of Deposition Temperature on Microstructures and Properties of MoSi<SUB>2</SUB> Coatings Prepared by Low Pressure Chemical Vapor Deposition

Effect of Deposition Temperature on Microstructures and Properties of MoSi<SUB>2</SUB> Coatings Prepared by Low Pressure Chemical Vapor Deposition